index.html

<!DOCTYPE html>
<html>

<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>Archives</title>
</head>

<body>
    <script>
        (async () => {
            const response = await fetch(`https://api.github.com/repos/${location.hostname.match(/(.*)\.github\.io/)[1]}${location.pathname.match(/\/.*\//)[0]}contents/`);
            const files = await response.json();
            const listElement = document.createElement("ul");
            for (const file of files) {
                if (file.name != "index.html") {
                    const itemElement = document.createElement("li");
                    const linkElement = document.createElement("a");
                    linkElement.href = file.path;
                    linkElement.textContent = file.name;
                    linkElement.target = "_blank";
                    itemElement.appendChild(linkElement);
                    listElement.appendChild(itemElement);
                }
            }
            document.body.appendChild(listElement);
        })();
    </script>

    <body>

</html>